replace magic numbers related to emp and explosion severity with defines (#26495)

replace even more magic emp and ex numbers

code/modules/mob/living/brain/robotic_brain.dm

@@ -160,12 +160,10 @@
 	if(!brainmob)
 		return
 	switch(severity)
-		if(1)
+		if(EMP_HEAVY)
 			brainmob.emp_damage += rand(20, 30)
-		if(2)
+		if(EMP_LIGHT)
 			brainmob.emp_damage += rand(10, 20)
-		if(3)
-			brainmob.emp_damage += rand(0, 10)
 	..()
 
 /obj/item/mmi/robotic_brain/New()

code/modules/mob/living/simple_animal/hostile/megafauna/ancient_robot.dm

@@ -600,8 +600,8 @@ Difficulty: Hard
 			if(mode == VORTEX)
 				var/turf/T = get_turf(src)
 				for(var/atom/A in T)
-					A.ex_act(3) //Body is immune to explosions of this strength.
-				T.ex_act(3)
+					A.ex_act(EXPLODE_LIGHT) //Body is immune to explosions of this strength.
+				T.ex_act(EXPLODE_LIGHT)
 			if(mode == CRYO)
 				var/turf/simulated/S = get_turf(src)
 				S.MakeSlippery(TURF_WET_ICE, enraged ? rand(25, 35 SECONDS) : rand(10, 20 SECONDS))

code/modules/mob/living/simple_animal/hostile/megafauna/colossus.dm

@@ -356,7 +356,7 @@ Difficulty: Very Hard
 /obj/item/projectile/colossus/on_hit(atom/target, blocked = 0)
 	. = ..()
 	if(isturf(target) || isobj(target))
-		target.ex_act(2)
+		target.ex_act(EXPLODE_HEAVY)
 		for(var/obj/machinery/light/L in range(2, src))
 			L.break_light_tube(0, 1) //No leaving lights floating their as colossus breaks the station
 	if(isliving(target))